Tracking China's methane emissions from wastewater: Inventories, driving forces, and mitigation potential

Abstract

China's rapid urbanization and burgeoning economy drove significant growth in sewage discharge, necessitating an examination of factors influencing wastewater methane emissions and mitigation measures. This study presented a comprehensive inventory of methane emissions in 31 provinces of China over a significant period. We developed a logarithmic mean divisor index (LMDI) model to reveal the driving forces behind emission changes. Methane emissions surged from approximately 1.4 Tg in 2000 to about 2.7 Tg in 2020, with treated domestic sewage being the fastest-growing source (49 Gg to 810 Gg). In 2020, the eastern, central, and southern regions contributed 61.7 % to total emissions. The increase in emissions was primarily driven by economic output, urbanization and population growth. This study forecasted future emission reduction potential, highlighting that reducing emission intensity (52.7 %) offered the most significant mitigation opportunities, followed by enhancing methane recovery (35.2 %). We recommended strengthening sewage discharge supervision and promoting biogas production.